jector

Simple, unobtrusive dependency injection.

Simple

Jector uses constructor injection to provide dependencies by mapping a function's argument names to values in the injection context. It provides powerful IoC constructs with a minimalist API.

Unobtrusive

Jector is designed to work along side your existing classes and module architecture. It doesn't require that you conform to a prescribed means of declaring modules or classes, relying instead on constructor argument names. (And even those can remain intact by using the minsafe alternative to dependency declaration).

Usage

Context Creation

jector.context(namespace)

Create a new injection context by providing a namespace. If the namespace has already been declared, the existing context is returned.

JavaScript:

var jector = require('jector');
var context = jector.context('myNamespace');
console.log(context.namespace); // output 'myNamespace'

CoffeeScript:

jector = require('jector')
context = jector.context('myNamespace')
console.log(context.namespace) # output 'myNamespace'

Singletons

context.singleton(dependencyName, constructorMethod)

singleton() declares a named Singleton. The constructorMethod (which may be a class constructor or any other function) is invoked the first time the dependency is requested, and the instance is retained.

JavaScript:

function Slab() {
  this.id = Math.random();
}

function Frame(slab) {
  this.slab = slab;
}

context.singleton('slab', Slab);
context.singleton('frame', Frame);

var frame = context.get('frame');
var slab = context.get('slab');

console.log(frame.slab === slab); // output 'true'

CoffeeScript:

class Slab
  constructor: -> @id = Math.random()

class Frame
  constructor: (@slab) ->

context.singleton('slab', Slab)
context.singleton('frame', Frame)

frame = context.get('frame')
slab = context.get('slab')

console.log(frame.slab is slab); # output 'true'

Factories

context.factory(dependencyName, factoryMethod)

factory() declares a factory method that will be invoked any time the named dependency is requested.

JavaScript:

function Slab() {
  this.id = Math.random();
}

function Frame(slab) {
  this.slab = slab;
}

context.singleton('slab', Slab);
context.factory('frame', Frame);

var frame1 = context.get('frame');
var frame2 = context.get('frame');

console.log(frame1 === frame2); // output 'false'
console.log(frame1.slab === frame2.slab); // output 'true'

CoffeeScript:

class Slab
  constructor: -> @id = Math.random()

class Frame
  constructor: (@slab) ->

context.singleton('slab', Slab)
context.factory('frame', Frame)

frame1 = context.get('frame')
frame2 = context.get('frame')

console.log(frame1 is frame2) # output 'false'
console.log(frame1.slab is frame2.slab) # output 'true'

Values

context.value(dependencyName, instance)

value() registers an existing instance as a named dependency for injection.

JavaScript:

function Slab() {
  this.id = Math.random();
}

function Frame(slab) {
  this.slab = slab;
}

var slab = new Slab()
context.value('slab', slab);
context.factory('frame', Frame);
var frame = context.get('frame');

console.log(frame.slab === slab); // output 'true'

CoffeeScript:

class Slab
  constructor: -> @id = Math.random()

class Frame
  constructor: (@slab) ->

slab = new Slab()
context.value('slab', slab)
context.factory('frame', Frame)

frame = context.get('frame')

console.log(frame.slab is slab) # output 'true'

Minsafe Dependency Declaration

Jector relies on constructor argument names to intuit an object's dependencies. Minification can obliterate those names. If you plan to minify your code, define a _needs Array on your constructor (or function), and this will be used instead of the function's argument names.

JavaScript:

function Slab() {
  this.id = Math.random();
}

function Frame(s) {
  this.slab = s;
}
Frame._needs = ['slab'];

var slab = new Slab()
context.value('slab', slab);
context.factory('frame', Frame);
var frame = context.get('frame');

console.log(frame.slab === slab); // output 'true'

CoffeeScript:

class Slab
  constructor: -> @id = Math.random()

class Frame
  constructor: (s) ->
    @slab = s
Frame._needs = ['slab']

slab = new Slab()
context.value('slab', slab)
context.factory('frame', Frame)
frame = context.get('frame')

console.log(frame.slab is slab) # output 'true'